This invention relates to the field of crankcase oil drain assemblies for the do-it-yourself market, and includes a disposable container in which to drain the oil plus a drain valve unit and a connecting hose.
A prior device of this type is disclosed in U.S. Pat. No. 3,727,638 issued to John P. Zaremba, Jr. et al., Apr. 17, 1973. In crankcase oil drain assemblies of this type, the original drain plug must be replaced with one having valve means and a connecting spout to which a flexible hose can be connected to carry the oil into the disposable container. One of the problems in replacing the original drain plug with a plug having valve means is being able to close the valve tightly enough to prevent any oil leakage and securely enough to prevent the valve from working loose as a result of vibrations occuring from movement of the vehicle.
The valve unit in U.S. Pat. No. 3,727,638 deals with this problem by providing a valve housing threadedly mounted in the crankcase opening, then using a threaded valve stem engaging the internally threaded wall of a central bore through the valve housing, the stem being rotatable by means of a wrench to open and close the valve.
Since this type of oil drain assembly is intended for the do-it-yourself market, the need for a particular type of wrench is an inconvenience. Furthermore, if one tries to use an adjustable wrench, there is a danger that the wrench would inadvertently engage the nut of the valve housing which lies closely adjacent to the nut of the threaded valve stem. Before realizing the mistake, one could break loose the valve housing which is supposed to be tightly screwed into the drain opening. If this happens inadvertently, the valve housing could later work its way completely out of the drain opening through vibrations while the vehicle is moving causing loss of the engine oil.
It is therefore desirable to provide a valve unit which may be operated between securely closed and fully open positions entirely by hand. This prevents inadvertently loosening the wrench tightened valve housing.
Another disadvantage of valve units of the type disclosed in U.S. Pat. No. 3,727,638 is that the inlet port of the valve housing tapers upward in a frusto-conical outer configuration. If the threaded walls of the tubular valve housing fully engages the corresponding internally threaded wall of the crankcase drain opening, which it must to be securely fastened, the upwardly tapered inlet port will protrude upwardly from the crankcase floor a certain distance. With such units, it is impossible to drain all of the old crankcase oil out of the crankcase. The most heavily contaminated oil also lies on the bottom of the crankcase floor, and it is this oil which such prior art units are unable to remove.
It is therefore desirable to provide a valve unit in a crankcase drain assembly which has a concave or inwardly tapered inlet port, and which also provides a valve housing with a threaded outer wall which can be fully engaged throughout the entire span of the corresponding internally threaded wall of the crankcase drain opening without protruding into the crankcase cavity above the level of the crankcase floor.